CN108375540A - For determining that the intrusive actively dynamic of ground friction coefficient is tested - Google Patents

Abstract

It is a kind of to include the following steps in the method for determining the friction coefficient (" ground μ ") between ground that wheel is contacted with wheel for testing：Based on to place interested assessment, at place interested by vehicle sensing visual cues assessment and/or at place interested to the assessment of signals of vehicles come calculate ground μ level of confidence and dispatch buses come at place interested execute actively dynamic test the step of.This method further comprises executing the step of actively dynamic is tested, wherein the test include at least one wheel that order vehicle executes vehicle propulsion torsion, regeneration torsion or braking torsion in it is one or more, from least one wheel receive measurement parameter during the test, and calculate the ground μ values in place interested.

Description

For determining that the intrusive actively dynamic of ground friction coefficient is tested

Introduction

The disclosure relates generally to Vehicular systems and operation.More specifically, this disclosure relates to one or more for determining The system and method for friction coefficient (μ) between a vehicle tyre and the ground of vehicle traveling.

The various power that vehicle is applied to during manipulation are transmitted by vehicle tyre.Therefore, in order to improve vehicle control system The performance of system, it is to be understood that tire is being taken turns at any time, in the case where road conditions (for example, weather, pavement material etc.) changes The ability of power is transmitted between tire and road.In view of vehicle manufacture industry is more and more interested in autonomous vehicle control system, in order to Keep safety, it is to be understood that deviate from the possible change of ecotopia to environment, situation is especially true.Therefore, current road conditions The estimation of instantaneous maximum friction coefficient and/or certainly determination are to be able to be best understood from environmental condition, and can make vehicle Performance preferably be directed to variation road conditions optimize.

Accordingly, it is desired to provide improved system and method come determine vehicle tyre and vehicle traveling ground between friction Coefficient.In addition, from subsequent detailed description and appended claims, in conjunction with attached drawing and the introductory section, other phases of the disclosure Features and characteristics are hoped to will become obvious.

Invention content

A kind of active dynamic test being used to determine the friction coefficient (" ground μ ") between the ground that wheel is contacted with wheel Method include the following steps：It determines to the assessment in place interested and at least one of following calculates based on for ground μ Ground μ level of confidence：To at place interested by vehicle sensing visual cues assessment and in place interested Assessment to signals of vehicles.Based on the relatively low ground μ level of confidence calculated, this method further comprises car hauler With at place interested execute actively dynamic test the step of.Based on the scheduling, this method further comprises executing active The step of dynamic is tested, the wherein test include that propulsion torsion, the regeneration at least one wheel that order vehicle executes vehicle are turned round Turn or braking torsion in it is one or more, and receive at least one measurements from least one wheel during the test and join Number.In addition, being based at least one measurement parameter, this method includes the steps that calculating the ground μ values in place interested.

Description of the drawings

The disclosure is described below in conjunction with the following drawings, wherein similar reference numerals indicate similar components, and wherein：

Fig. 1 is the method flow diagram of the method provided according to some embodiments of the present disclosure；

Fig. 2 illustrates the estimation ground friction as outside air temperature and the function of rainwater intensity or wiper working cycles 3-D graphic；

Fig. 3 is illustrated for using outside air temperature data and wiper activity data or rain sensor data as progress The actively method of a part for the determination of test；

Fig. 4 illustrates negative torque/regeneration test program；

Fig. 5 illustrates positive torque test program when stationary vehicle；

Positive torque test program when Fig. 6 illustrates stationary vehicle and is applied with non-driven wheel brake；

Fig. 7 illustrates positive torque test program when vehicle movement；

Fig. 8 is the method flow diagram for the method for the positive torque test program illustrated in Fig. 4 to 7；

Fig. 9 A illustrate the relationship between braking moment and wheelslip under the background that braking moment is tested, and Fig. 9 B are said The relationship between brake pressure and actual ground μ under the background that braking moment is tested is illustrated；

Figure 10 is the method flow diagram for the method tested for braking moment；

Figure 11 is the system diagram of autonomous vehicle control system；And

Figure 12 is the diagram about measurement and calculating based on applied variable and the friction coefficient of measurand.

Specific implementation mode

The following detailed description is merely exemplary in nature, and is not intended to limit the disclosure or disclosed system With the application and use of method.In addition, it is undesirable to by the introductory section of front or any reason of middle presentation described in detail below The limitation of opinion.

The disclosure usually provides intrusive active dynamic testing method (and related system) to determine in vehicle tyre on ground Ground friction coefficient under the background travelled on face.In the disclosure, using heuritic approach come be based on such as will below more in detail The various methods carefully described estimate surface friction coefficient, and determine the level of confidence of these estimated values.When confidence level foot It is enough low and during driving intrusive actively dynamic test safety and suitable for when, asked from vehicle control system intrusive main Dynamic test is to reach the target of determining road surface coefficient friction (μ) estimated value for certain.When needed, intrusive actively dynamic Test can be used steering and/or braking system actuator that the interference of specific controlled force is applied to tire/road contact zone.It is logical Cross the reaction to the applied force by measuring signal observation wheel and Vehicular system, it may be determined that the estimated value of ground μ.Therefore, relatively It reacts completely in practical road surface μ, the disclosure determines road surface μ using active method.

Fig. 1 is the method flow diagram of the method 100 provided according to some embodiments of the present disclosure.Frame 101,102 and 103 is μ estimates frame, and provides the initial information source for generating initial μ estimated values for locality about system thereon.At frame 101, System evaluation place.The first aspect of place assessment is the event for preparing that ground μ may be needed to confirm, such as expressway exit Ramp or ground μ other terrain surface specifications of special interest to the safety operation of vehicle.Such preparation can determine ground spy Sign is expected to be originated in the presence of travel route along vehicle, this is determined according to road surface database.Second of place assessment Aspect using from can remote access " cloud " type data-storage system information.It may be the case that：Involved vehicle is A part for the fleet of other vehicles (such as autonomous vehicle).Situation more may be：Other vehicles in fleet are passed through recently Place experienced low land face μ conditions near crossing.Therefore, in this case, involved vehicle can be deposited from cloud type data Storage system remote access simultaneously obtains the information.For example, when being confident of obtaining information from fleet, place μ estimations can be therefore adjusted Value.However, if fleet data is insufficient or had been subjected to a very long time since obtaining nearest fleet data, it can It can reduce the conjecture to the low ground μ.Other purposes of cloud type data include the variation of weather forecast, this may be to cause ground The reason of μ conjecture variations.It is place to use information and weather conjecture in terms of the third of place assessment.For example, in cold and tide During wet weather condition, the ground such as parking lot and bridge may be hypothesized with relatively low ground μ.The 4th of place assessment Aspect be using based on the road surface estimated value generated due to the previous history travelled on the ground location information or from reflecting Penetrate the location information of the known road type of data.For example, the granular-type road known from previous traveling or mapping data or Rugged road may be hypothesized with relatively low ground μ.

At frame 102, system evaluation visual cues.Autonomous vehicle generally includes various visual sensors (such as camera) To assist the safety operation of vehicle.Assessment frame 102 background under, these visual sensors can be used assess it is to reduction or The conjecture of low ground μ.For example, when be detected due to the obstruction (for example, sensors clean is caused to be asked) of sensor rainwater, When ice or snow, visual cues can cause the conjecture of low land face μ values.In another example, when visual sensor detects road surface This conjecture may be present when bleaching, this may be the hypothesis for having one layer of snow on ground.In still another example, work as visual sensing Device, which detects, may be present this conjecture when road surface becomes glossy, this may be the hypothesis for having one layer of ice on ground.

At frame 103, system evaluation signals of vehicles.Various Vehicular systems can be associated with relatively low ground μ conditions.For example, Signals of vehicles may include the activation of rain detecting sensor and/or windscreen wiper.In another example, signals of vehicles It may include the detection of outside air temperature and/or outer moisture.In still another example, signals of vehicles may include tire temperature.This Each of a little signals can be suitably used for inferring the presence of the atmospheric conditions for the conjecture that can be shown that relatively low ground μ conditions.

Another aspect of the present disclosure is to infer pavement friction by monitoring rainwater intensity and outside air temperature.It is raining but is comparing When warmer, ground is considered to have appropriate friction level.When rainy/moist and cold, it is believed that ground friction is relatively low.This It is disclosed this on the other hand by the data fusion of rainwater and external temperature sensor on vehicle to predict pavement friction.Such as Fruit rain sensor is unavailable, then rainwater intensity can be determined according to windscreen wiper activity.For example, Fig. 2 is illustrated The 3-D graphic 200 of estimation ground friction as outside air temperature and the function of rainwater intensity or wiper working cycles.The figure Shape is provided for one hypothesis relationship of explanation, and needs to determine between variable for specific type of vehicle in actual use Actual relationship.The logic may further be used to the active for determining when to carry out ground friction via braking, propulsion or steering intervention Test.For example, Fig. 3 illustrate for use outside air temperature data and wiper activity data or rain sensor data as into The method 300 of a part for the determination that row is actively tested.Frame 301 indicates that the input of outside air temperature, frame 302 indicate windshield rain Curette activity, and frame 303 indicates rain sensor.Rainwater intensity can be inferred according to frame 302 or frame 303 at frame 304.In frame At 305, rainwater intensity and temperature are fed to estimate that road surface is rubbed by searching for table (for example, in the form of relationship shown in Fig. 2) It wipes.

It continues to refer to figure 1, based on the information of acquisition/determination at frame 101 to 103, system can calculate ground at frame 104 μ confidence levels.For example, when the following conditions are met, it is believed that the confidence level of ground μ is relatively low.As first condition, vehicle should Far distance has been travelled since the last affirmative of ground μ determines.The distance travel value can be based on system requirements come really It is fixed.As second condition, there should be the conjecture of relatively low ground μ.Based on such as frame 101, when the height at place interested When guessing that ground μ is relatively low, this conjecture can be met.Alternatively there are (such as roots in the case of the instruction of low μ in visual cues Derived according to frame 102) and further the weather condition of measurement (such as according to frame 103 derive) reasonably imply may be present it is relatively low In the case of the μ of ground, this conjecture can be met.

As explained further in Fig. 1, frame 105 and 106 determines the suitable of the active friction coefficient test for carrying out vehicle Property and safety.Reference block 105, based on the following factors it is believed that it is suitable actively to test.First, when there is no passenger in vehicle In when driving, it is typically preferably to execute actively intrusive test.Secondly, it should be appreciated that certain situations are for certain Actively for test more suitable (type of test will be discussed in greater detail below).Therefore, the factor of adaptation is to consider spy Best test of the fixed test-types as specific condition.

Reference block 106, based on (i.e., if meet following security consideration) considered below it is believed that it is safety actively to test 's.First, it should be determined that autonomous driving system is intended that stable driving, such as does not turn to significantly in the near future. Secondly, it should be determined that neighbouring wagon flow is minimum, including considers any cross traffic or barrier.Third, it should be determined that at a distance of institute Any vehicle of the vehicle front or rear that are related to is at a distance sufficiently large, this can be determined based on system requirements.4th, it should be true Speed is determined in tolerance interval, this can equally be determined based on system requirements.

The another aspect of system shown in Fig. 1 be at frame 107 active test (based on from frame 104 confidence level, come From the suitability of frame 105 and the safety based on frame 106) scheduling.For example, being when ground μ confidence levels are low and execute test When safe, it should ask actively to test.It is contemplated that Current vehicle conditions and determining certain kinds about the information of suitability The test of type, either braking test, slew test when promoting torque testing, is static or other types of test (will be It is more thoroughly discussed below).

It continues to refer to figure 1, in request, according to the control of frame 108,109 and 110, executes and assess actively intrusive test. First, reference block 108 are based on requested test-types (such as according to frame 107), control active test.In general, can Test is executed based on any combinations of vehicle command (such as acceleration, regeneration, braking and wheel steering).Based on these lives It enables, wheel torque (promote, braking, regenerate) can be directed to, acceleration (is linear for vehicle and is for wheel Angle), speed (be linear for vehicle and be angle for wheel), yaw, various pressure and power etc. Test is made to measure.In order to be more completely understood, various types of test methods are as follows.

In one example, actively test can be the propulsion torque testing ordered.In the test sample, order can be used Propulsion torque measured to complete active ground μ, which slowly promotes propulsion or regenerative torque up to reaching setting value, Or until wheelslip is observed on driven shaft to measure ground mu-factor or to infer that it is higher than crystal seed value.What is applied turns Square can be positive (advance command) or negative (regeneration " regen " order).Therefore, the purpose that proactive command boost torque is promoted is intentional Know ground and find that driven tire starts the point of sliding, this will accurately measure ground mu-factor.This type is provided with reference to Fig. 4 to 7 The various examples of the active test of type.

Fig. 4 illustrates negative torque/regeneration test program.Fig. 5 illustrates positive torque test program when stationary vehicle.Fig. 6 Positive torque test program when illustrating stationary vehicle and being applied with non-driven wheel brake.When Fig. 7 illustrates vehicle movement Positive torque test program.In addition, Fig. 8 is the method stream for the method 800 of the positive torque test program illustrated in Fig. 4 to 7 Cheng Tu.First, with reference to figure 4, vehicle 410 is illustrated as on ground 405, and wherein the front-wheel 415 of vehicle is in when driving in advance Regeneration mode.In conjunction with Fig. 4, at the row 810 of Fig. 8 and at frame 811, determined based on previously described ground μ estimated values The maximum regeneration torque to be applied and rate.At frame 812, regeneration request is sent to vehicle control system, this will be below More detail discussion is carried out in conjunction with Figure 11.At frame 813, system monitors wheel speed sensors for wheelslip.If realized Wheelslip or if realizing maximum regeneration torque target stops test.Then, at frame 814, wheelslip is calculated With ground μ and be reported to ground μ and estimate/test system.

Secondly, with reference to figure 5, vehicle 410 is illustrated as on ground 405, and wherein the front-wheel 415 of vehicle is in just when static Torque conditions and desired movement direction are to advance.In conjunction with Fig. 5, at the row 820 of Fig. 8 and at frame 821, based on previous description Ground μ estimated values promote torque and rate to determine to be applied maximum.At frame 822, it is ensured that speed is less than speed limit (that is, being ideal velocity when static) and vehicle is directing forwardly.At frame 823, request will be promoted to be sent to vehicle control system. At frame 824, system monitors wheel speed sensors for wheelslip.If realizing wheelslip or if realizing torque capacity Target, then stopping test.Then, at frame 825, wheelslip and ground μ is calculated and is reported to ground μ estimations/survey Test system.

Third, with reference to figure 6, vehicle 410 is illustrated as on ground 405, and wherein the front-wheel 415 of vehicle is in just when static It is to advance that torque conditions and trailing wheel 420, which have been applied in their brake and desired movement direction,.In conjunction with Fig. 6, in the row of Fig. 8 At 830 and at frame 831, the maximum propulsion torque to be applied and rate are determined based on previously described ground μ estimated values. At frame 832, the vehicle control system of trailing wheel 420 will be sent to the request that brake pressure is established.At frame 833, it will promote Request is sent to the vehicle control system of front-wheel 415.At frame 834, system is for wheel speed sensors before wheelslip monitoring.Such as Fruit realizes wheelslip or if realizing torque capacity target, stops test.Then, at frame 835, wheel is calculated Sliding and ground μ are simultaneously reported to ground μ and estimate/test system.

4th, with reference to figure 7, vehicle 410 is illustrated as on ground 405, and wherein the front-wheel 415 of vehicle is in vehicle and advances In rotating forward moment condition when movement.In conjunction with Fig. 7, at the row 840 of Fig. 8 and at frame 841, it is based on previously described ground μ Estimated value promotes torque and rate to determine to be applied maximum.At frame 842, the vehicle for asking to be sent to front-wheel 415 will be promoted Control system.At frame 843, system is for wheel speed sensors before wheelslip monitoring.If realizing wheelslip or such as Fruit realizes torque capacity target, then stopping test.Then, at frame 844, wheelslip and ground μ are calculated and by its time It reports to ground μ and estimates/test system.

In another example, relative to the propulsion torque testing of order, actively test can be that the braking moment of order is surveyed Examination.In the test sample, the braking moment of order can be used and measured to complete active ground μ, which attempts in vehicle A trailing wheel is caused to generate wheelslip when in moving forwardly.It, can be according in vehicle if detecting wheelslip The braking moment applied at wheel slip point determines ground μ.Therefore, the test method using only needing a wheel unstable and It is not the active measurement of two wheels or the unstable pavement friction of entire vehicle.In addition, test can be run as needed, and It does not need driver or autonomous system executes certain manipulation.Finally, braking moment can be offset by applying positive propulsion torque, because There is no slow down to interfere for this.

Fig. 9 A illustrate the relationship between braking moment and wheelslip under the background that braking moment is tested, and Fig. 9 B are said The relationship between brake pressure and actual ground μ under the background that braking moment is tested is illustrated.Figure 10 is surveyed for braking moment The method flow diagram of the method 1000 of examination.Turn first to Fig. 9 A and 9B, it should be apparent that, as shown in the figure 901 of Fig. 9 A, For with the wheel of fairly constant angular speed rotation, brake wheel slip condition can be indicated by the unexpected decline of angular speed. In order to cause the wheelslip, the braking moment at involved wheel can be steadily increased until ground is grabbed in the ground more than wheel Power.Therefore, as shown in Fig. 9 B (figure 902), cause braking moment the brake pressure being applied at wheel can directly with The ground grip of wheel is related, and therefore related to ground μ.

Using these principles, flow chart shown in Figure 10 starts at frame 1001：The braking control of order vehicle control system Device processed applies one or more rear wheel brakes.At frame 1002, braking moment is applied to wheel with specified advancing the speed.It answers When it is noted that additional positive propulsion torque can be needed at driving wheel so as to balancing brake torque and prevent vehicle from testing Period slows down.Hereafter, at frame 1003, whether progress vehicle is unstable or the initial true of Driver override whether has been received It is fixed.If it is then as indicated to stop to test immediately at frame 1004.If vehicle stabilization and do not received from driver super It speeds order, then as indicated at frame 1005, determines whether wheelslip is more than the scheduled maximum allowable limit.If so, that At frame 1006, the ground limit is had been detected by, and the estimation of ground μ can be carried out.If not, so at frame 1007, into One step determines whether braking moment is more than the scheduled maximum allowable limit.If it is then at frame 1008, when pavement friction height In can terminate to test when test limits.If not, so continuing growing torque until being made at frame 1003,1005 or 1007 willing It is fixed to determine.

It is back to Fig. 1, especially indicates the frame 109 of " actuator " control, it should be apparent that, in discussion in front, Vehicle control system is to combine to promote order, the reference of rendering commands and brake command.Thus, it should be apparent that, the vehicle Control system may include a part for whole autonomous vehicle control system, is made of it or is its part with person, such as combine Figure 11 It further describes.More specifically, the embodiment of autonomous vehicle 1100 is shown in FIG. 11.Vehicle 1100 is included at least for moving The autonomous operation system 1110 of motor-car 1100.Autonomous operation system 1110 includes the steering wheel 1116 for controlling vehicle 1100 Steering module 1112 and controller 1114.Operating system 1110 further comprises the speed changer 1126 for controlling vehicle 1100 Drive module 1122 and controller 1124.Steering module 1112 can be electronic module or similar device, can be via vehicle Steering wheel by steering wheel 1116 turn to without driver steering demand.Controller 1114 is to such as conventional electrical power The steering modules such as steering module 1112 provide control input signal, with the steering of the control direction disk during manipulation.Controller 1114 can detach with steering module 1112, or can be used as individual unit and be integrated in steering module 1112.Drive module 1122 can For electronic module or similar device, speed changer can be engaged forward or backwards via the shifter of transmission of vehicle 1100 1126 without operator demand.Controller 1124 is defeated to the offer control of the drive modules such as conventional electrical drive module 1122 Enter signal, to control the movement that moves forward and backward of vehicle 1100 during parking manoeuvres.Controller 1124 can be with drive module 1122 separation, or can be used as individual unit and be integrated in drive module 1122.

Autonomous operation system 1110 further comprises sensing device further 1118 to detect and the object close to driven vehicle 1147 and position mark indicator 1148.As used herein, term " object " refer to can be vehicle 1100 path in barrier Hinder any three-dimension object of object.If further used herein, term " position mark indicator " refers to for being carried for vehicle 1100 Any symbol of position for reference, lane line, arrow, number etc..Sensing device further 1118 detects the object of lateral run-out vehicle It the presence of body 1147 and position mark indicator 1148 and is not present, with the appropriate path of determination.Sensing device further 1118 may include base In the sensing device further of radar, sensing device further based on ultrasound, the sensing device further based on imaging or it is capable of providing characterization object The similar device of the signal of free space or reference position mark indicator 1148 between 1147.Sensing device further 1118 and control The communication of device 1114 to controller 1114 to provide signal.Sensing device further 1118 can determine that respective objects 1147 or position mark refer to Show the distance between device 1148 and identified distance is sent to controller 1114 or sensing device further 1118 can be to controller 1114 offer signals are so that controller 1114 is using determining the spacing between object 1147 or position mark indicator 1148 Distance.

In addition, vehicle 1100 includes telematics unit 1135.Network connection or vehicle bus 1136 are operationally It is attached to telematics unit 1135.The example of suitable network connection includes that controller zone network (CAN), media are led To system transfer (MOST), local interconnection network (LIN), Ethernet and meet known ISO, SAE and ieee standard and rule Other appropriate connections of model, name just a few.Vehicle bus 1136 enables vehicle 1100 that will come from telematics unit 1135 signal sends and receives to the various equipment and system unit in 1100 outside of vehicle and vehicle 1100, various to execute Function is such as communicated with above-mentioned " cloud " type data-storage system.Telematics unit 1135 generally includes electron process dress 1137 are set, which is operably coupled to electronic memory 1138, the honeycomb core of one or more types Piece collection/component 1139, radio modem 1140, the navigation elements comprising position detection are (for example, global positioning system (GPS)) chipset/component 1141, real-time clock (RTC) 1142, short distance radio communication network 1143 (for example, bluetooth unit) And/or double antenna 1144.

Now referring back to Fig. 1 and especially frame 110, based on the active executed as above according to the description of frame 107 to 109 Test can perform the assessment to test result to determine ground μ.Various computational methods are well known in the art.For example, figure 12 be (to notice that positive/negative torque needs about the diagram of measurement and calculating based on following applied variable and the ground μ of measurand Want sign change)：

Just before sliding：

F_Friction=F_Normally*μ

In sliding or recovery：

Under any circumstance, persons skilled in the art should all fully understand tire tribophysics on ground and The rotation physics of wheel.Therefore, based on test program detailed above and thus obtained physical measurements values, it is expected that Persons skilled in the art will derive ground μ in a suitable manner using the basic principle of physics, regardless of whether root According to the equation illustrated above in association with Figure 12.

About the above-mentioned calculating of progress, and the data processing that all steps for relating more generally to combined method 100 carry out, Suitable vehicle will be configured with one or more computer processors.This processor can use general processor, content addressable Memory, digital signal processor, application-specific integrated circuit, field programmable gate array, any suitable programmable logic device, Discrete gate or transistor logic, discrete hardware components or be designed to execute any combinations of functions described herein implementing or It realizes.Processor device can be implemented as microprocessor, controller, microcontroller or state machine.In addition, processor device can quilt Be embodied as the combination of computing device, for example, the combination of digital signal processor and microprocessor, the combination of multi-microprocessor, One or more microprocessors combined digital signal processor core or any other such configuration.Processor includes such as plate Carry the non-transitory memories such as RAM (random access memory) and onboard ROM (read-only memory).The program of control processor refers to Order is storable in RAM or ROM, or is stored in RAM and ROM.For example, in what a rigid possible example, operating system Software can be stored in ROM, and various operation mode software routines and various operating parameters can be stored in RAM.It should It is realized that this is only the example of a scheme of processor, and it can alternatively or additionally implement various other schemes.

It continues to refer to figure 1, the result of performed test or (if confidence level is high and is not carried out test) ground μ estimate The result or the two of meter can be used (frame 111) based on control of the amendment estimation to its performance in conjunction with vehicle.For example, for The speed of low land face μ, vehicle can turned to, travelled on bridge, exited on the slope, subtracted before driving etc. in parking lot It is small.That is, vehicle performance capabilities value is lowered at the place and is implemented around higher safety margin.In addition, can Alternative route is designed to avoid the low land face places μ.It otherwise, can be assuming that normal in the case where it is high to estimate/determine ground μ Performance capability in the case of carry out vehicle operating.

As additional things, it is noted that frame 112 about ground μ confidence levels and is assessed (test) with reference to transmission Ground μ information to " cloud " type storage device.As mentioned previously, such memory in combination with can often identical or The fleet travelled on similar path is used together.Therefore, the result of any active intrusive mood test can it is as discussed above as quilt It is transmitted to cloud storage system to assess for other fleet vehicles, or for providing information to other fleet vehicles, which permits Perhaps they select replacement/better path to travel.

Therefore, this disclosure describes the uses of heuritic approach to collect information from various sources, these sources itself are not It is determined with enough integralities to make driving, but these signals can generate more preferable information when collecting and handling together. However, when information it is still inadequate but about can cause due to ground μ reduce cause vehicle capability reduce trend prompt When sufficient, schedulable actively intrusive test, the purpose is to test the hypothesis of ground μ reductions.Therefore, the disclosure is advantageously can Vehicle safety is improved during the reduction ability driving condition of energy, this makes it possible to expand the use case for autonomous driving, This again improves user satisfaction.

Although at least one exemplary system for determining friction coefficient has been proposed in the previous detailed description And method, it should be appreciated that, there are a large amount of variations.It should also be appreciated that the example for determining friction coefficient Sexual system and method are only example, and are not intended to limit the scope of the present disclosure in any way, applicability or configuration.Truth It is to be detailed above to provide for implementing the exemplary of the friction coefficient for determining the disclosure to those skilled in the art The convenient guide of method.It should be understood that the feelings of the scope of the present disclosure illustrated in not departing from such as appended claims Under condition, it can be carried out in terms of the function and arrangement of the element described in the exemplary system and method for determining friction coefficient each Kind changes.

Claims (10)

1. it is a kind of for actively dynamic test to determine the friction coefficient (" ground μ ") between ground that wheel is contacted with wheel Method the described method comprises the following steps：

It determines to the assessment in place interested based on for ground μ and at least one of following calculates ground μ level of confidence： The assessment of the visual cues sensed by the vehicle at the place interested and in the place interested to vehicle The assessment of signal；

Based on the relatively low ground μ level of confidence calculated, the vehicle is dispatched to be held at the place interested Row actively test by dynamic；

Based on the scheduling, the step of active dynamic is tested is executed, is executed wherein the test bag includes vehicle described in order It is one or more in propulsion torsion, regeneration torsion or the braking torsion of at least one wheel of the vehicle；

During the test at least one measurement parameter is received from least one wheel；And

Based at least one measurement parameter, the ground μ values in the place interested are calculated.

2. according to the method described in claim 1, the wherein described vehicle includes autonomous driving control system, and can without Operating personnel operate in the case of intervening.

3. according to the method described in claim 1, the wherein described assessment put with interest includes being received from another vehicle About the report of the ground μ at the place interested, the report is obtained via cloud type data-storage system, described Cloud type data-storage system can be by multiple vehicle access in fleet.

4. according to the method described in claim 1, the wherein described assessment put with interest includes that acquisition is described interested The weather forecast in place or the road surface types for determining the place interested.

5. according to the method described in claim 1, the assessment of the wherein described visual cues includes detection visual sensor barrier Hinder object, or detection white pavement situation or glossiness pavement behavior.

6. according to the method described in claim 1, the assessment of the wherein described signals of vehicles includes detecting to sense by rainwater Device, windscreen wiper, outside air temperature, outer moisture and tire temperature are one or more in rainwater to detect.

7. according to the method described in claim 1, wherein having been travelled since a preceding ground μ is determined based on the vehicle predetermined Distance calculates the relatively low ground μ confidence levels, and the assessment based on the place interested, vehicle letter Number the assessment and the visual cues the assessment in it is one or more, there is guessing to relatively low ground μ It surveys.

8. according to the method described in claim 1, before dispatching the vehicle, carries out Security of test determination and test is suitable Property determine in it is one or more.

9. described to push away according to the method described in claim 1, wherein in engagement or in the case of do not engage non-driving wheel brake Into torque executed in the vehicle movement or when the vehicle remains static.

10. according to the method described in claim 1, by described when wherein braking torsion is in the vehicle movement Either one or two trailing wheel of vehicle applies the torque of incrementss to execute, wherein providing that the braking moment only needs to be applied in To a vehicle rear wheel.